FACE AND FRONTAL REGION OF HEAD 123 



the lower and medial part of the corresponding frontalis. 

 It descends over the nasal bone and ends on the dorsum 

 of the nose, where some of its fibres blend with the trans- 

 verse part of the nasalis and others are inserted into the skin. 



Along the lower and medial border of the orbicularis oculi 

 will be found the muscles of the nose and the upper lip. 



The proper muscles of the nose are the musculus nasalis 

 and the musculus depressor septi, but the procerus may also 

 be looked upon as partly a nasal muscle, and the angular 

 head of the quadratus labii superioris has a nasal attachment. 



Musculus Nasalis. The musculus nasalis consists of two 

 parts, the pars transversa (O.T. compressor nan's), and the 

 pars alaris (O.T. dilator nan's). The pars transversa springs 

 from the root of the frontal process of the maxilla, passes 

 across the cartilaginous part of the nose, above the ala, and 

 ends in an aponeurosis which connects it with its fellow of 

 the opposite side. The pars alaris springs from the maxilla, 

 at the side of the lower part of the anterior nasal aperture, 

 and it terminates in the posterior part of the ala and the 

 mobile part of the septum of the nose. The nasalis is partly 

 concealed by the medial fibres of the quadratus labii superioris. 



Musculus Depressor Septi Nasi. This small muscle is 

 frequently difficult to display. It springs from the superficial 

 fibres of the upper part of the orbicularis oris, and is inserted 

 into the anterior part of the septum of the nose. It depresses 

 the septum and reduces the antero-posterior diameter of the 

 anterior nasal aperture. 



After the muscles of the nose have been examined clean 

 the superficial muscles of the mouth and cheek. 



The Muscles of the Mouth and Cheeks. The muscles of 

 this group form two layers, a superficial and a deep. Those 

 of the superficial group are the orbicularis oris, quadratus 

 labii superioris, zygomaticus, triangularis, risorius, quadratus 

 labii inferioris ; those of the deeper group are the buccinator, 

 caninus, incisivi and mentalis. All, with the exception of the 

 orbicularis oris, are bilateral. The members of the superficial 

 group must be examined first ; the deeper muscles will be 

 displayed after the superficial vessels and nerves have been 

 dissected. 



Orbicularis Oris. The orbicularis oris is the sphincter 

 muscle of the oral aperture. It lies in the substance of the 

 lips, and consists of a deeper layer of fibres which are arranged 



